vtkPStreamTracer: conditionalize functions

These functions are only called if DEBUGTRACE is defined, so only define
them in that case as well.

Change-Id: I5766ec8c37727cee1efffb8c72d1a5c5efb2b49c
vtkPTemporalStreamTracer: remove useless code

Change-Id: I553b29e31696da35e96d1264135d37bd332b2fab
unused: add a macro to mark functions as "unused"

In template implementations, some specializations or overloads may not
be used, so decorate them as such to avoid "unused function" warnings.

Change-Id: I42347a4f3e046d29c2856e84b96eac198bf448da
Merge topic 'more-dashboard-warnings' into master

f36df9ca unused: add a macro to mark functions as "unused"
8a5c8c1c vtkPTemporalStreamTracer: remove useless code
5183d0f6 vtkPStreamTracer: conditionalize functions